U.S. patent number 7,757,753 [Application Number 12/040,612] was granted by the patent office on 2010-07-20 for multichannel heat exchanger with dissimilar multichannel tubes.
This patent grant is currently assigned to Johnson Controls Technology Company. Invention is credited to Dan R. Burdette, Kevin E. Keller, William L. Kopko, Jeffrey N. Nichols, Charles B. Obosu, Jeffrey Lee Tucker, Mahesh Valiya-Naduvath, Jose Ruel Yalung de la Cruz, Mustafa K. Yanik.
United States Patent |
7,757,753 |
Yanik , et al. |
July 20, 2010 |
Multichannel heat exchanger with dissimilar multichannel tubes
Abstract
Heating, ventilation, air conditioning, and refrigeration
(HVAC&R) systems and heat exchangers are provided which include
dissimilar internal configurations. The heat exchangers include
multiple sets of multichannel tubes in fluid communication with
each other. One set of multichannel tubes contains flow channels of
one shape and size while the another set of multichannel tubes
contains flow channels of a different shape and/or size. The
dissimilar flow channels within the multichannel tube sets allow
each set of tubes to be configured to the properties of the
refrigerant flowing within the tubes.
Inventors: |
Yanik; Mustafa K. (York,
PA), Tucker; Jeffrey Lee (Wichita, KS), Valiya-Naduvath;
Mahesh (Lutherville, MD), Burdette; Dan R. (Wichita,
KS), Obosu; Charles B. (Wichita, KS), Nichols; Jeffrey
N. (Wichita, KS), Kopko; William L. (Jacobus, PA),
Yalung de la Cruz; Jose Ruel (Dover, PA), Keller; Kevin
E. (Wichita, KS) |
Assignee: |
Johnson Controls Technology
Company (Holland, MI)
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Family
ID: |
39273575 |
Appl.
No.: |
12/040,612 |
Filed: |
February 29, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080142203 A1 |
Jun 19, 2008 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/US2007/085262 |
Nov 20, 2007 |
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60909598 |
Apr 2, 2007 |
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60882033 |
Dec 27, 2006 |
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60867043 |
Nov 22, 2006 |
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Current U.S.
Class: |
165/174;
165/176 |
Current CPC
Class: |
B23K
1/0012 (20130101); B23K 1/008 (20130101); F28D
1/05391 (20130101); F28F 9/262 (20130101); F28D
1/0417 (20130101); F25B 39/00 (20130101); F28D
2021/007 (20130101); B23K 2101/14 (20180801); Y10T
29/4935 (20150115); F28D 2021/0071 (20130101); F28F
2210/08 (20130101); F28D 2001/0273 (20130101); Y10T
29/53117 (20150115) |
Current International
Class: |
F28F
9/02 (20060101); F28D 7/06 (20060101) |
Field of
Search: |
;165/140,146,174,175,176,178 ;62/507,509 |
References Cited
[Referenced By]
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Other References
US. Appl. No. 12/040,501, filed Feb. 29, 2008, Tucker et al. cited
by other .
U.S. Appl. No. 12/040,559, filed Feb. 29, 2008, Knight et al. cited
by other .
U.S. Appl. No. 12/040,588, filed Feb. 29, 2008, Valiya-Naduvath et
al. cited by other .
U.S. Appl. No. 12/040,661, filed Feb. 29, 2008, Yanik et al. cited
by other .
U.S. Appl. No. 12/040,697, filed Feb. 29, 2008, Yanik et al. cited
by other .
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by other .
U.S. Appl. No. 12/040,743, filed Feb. 29, 2008, Breiding et al.
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U.S. Appl. No. 12/040,764, filed Feb. 29, 2008, Knight. cited by
other.
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Primary Examiner: v Duong; Tho
Attorney, Agent or Firm: Fletcher Yoder
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims priority from and the benefit of U.S.
Provisional Application Ser. No. 60/867,043, entitled MICROCHANNEL
HEAT EXCHANGER APPLICATIONS, filed Nov. 22, 2006, U.S. Provisional
Application Ser. No. 60/882,033, entitled MICROCHANNEL HEAT
EXCHANGER APPLICATIONS, filed Dec. 27, 2006, and U.S. Provisional
Application Ser. No. 60/909,598, entitled MICROCHANNEL COIL HEADER,
filed Apr. 2, 2007, which are hereby incorporated by reference.
Claims
The invention claimed is:
1. A heat exchanger comprising: a first manifold; a second
manifold; a first multichannel tube in fluid communication with the
first manifold and the second manifold and including a plurality of
generally parallel flow paths extending therethrough having a first
configuration; a second multichannel tube in fluid communication
with the first manifold and the second manifold and including a
plurality of generally parallel flow paths extending therethrough
having a second configuration different from the first
configuration; and a pair of baffles in the first manifold to
isolate at least one multichannel tube between the baffles of the
pair, wherein the pair of baffles is disposed between the first
multichannel tube and the second multichannel tube, and wherein the
at least one multichannel tube is isolated within the first
manifold only; wherein the second manifold is configured to direct
a fluid exiting the first multichannel tube directly into both the
at least one isolated multichannel tube and the second multichannel
tube.
2. The heat exchanger of claim 1, wherein the flow paths of the
first multichannel tube are smaller than the flow paths of the
second multichannel tube.
3. The heat exchanger of claim 1, wherein the flow paths of the
first multichannel tube are of different cross-sectional shape than
the flow paths of the second multichannel tube.
4. The heat exchanger of claim 1, wherein the first multichannel
tube has more flow paths than the second multichannel tube.
5. The heat exchanger of claim 1, comprising a plurality of the
first multichannel tubes in fluid communication with the first
manifold and the second manifold, and a plurality of the second
multichannel tubes in fluid communication with the first manifold
and the second manifold.
6. The heat exchanger of claim 1, wherein the pair of baffles is
configured to force inlet flow introduced into the first manifold
through the first multichannel tube to the second manifold and to
separate the inlet flow from outlet flow exiting from the second
multichannel tube.
7. A heat exchanger comprising: a first manifold; a second
manifold; a plurality of first multichannel tubes in fluid
communication with the first manifold and the second manifold, each
first multichannel tube including a plurality of generally parallel
flow paths extending therethrough having a first configuration; a
plurality of second multichannel tubes in fluid communication with
the first manifold and the second manifold, each second
multichannel tube including a plurality of generally parallel flow
paths extending therethrough having a second configuration
different from the first configuration; a pair of baffles spaced
from one another in the first manifold to create a volume
therebetween and to divide the first manifold into a first section
in fluid communication with the plurality of first multichannel
tubes and a second section in fluid communication with the
plurality of second multichannel tubes; and at least one isolated
multichannel tube disposed between the plurality of first
multichannel tubes and the plurality of second multichannel tubes
and disposed between the baffles of the pair, wherein the at least
one isolated multichannel tube is isolated within the first
manifold only; wherein the second manifold is configured to direct
a fluid exiting the plurality of first multichannel tubes directly
into both the at least one isolated multichannel tube and the
plurality of second multichannel tubes.
8. The heat exchanger of claim 7, wherein the plurality of first
multichannel tubes are disposed adjacent to one another and the
plurality of second multichannel tubes are disposed adjacent to one
another.
9. The heat exchanger of claim 7, wherein the flow paths of the
first multichannel tubes are smaller than the flow paths of the
second multichannel tubes.
10. The heat exchanger of claim 7, wherein the flow paths of the
first multichannel tubes are of different cross-sectional shape
than the flow paths of the second multichannel tubes.
11. The heat exchanger of claim 7, wherein the first multichannel
tubes have more flow paths than the second multichannel tubes.
12. The heat exchanger of claim 7, wherein the pair of baffles is
configured to force inlet flow introduced into the first manifold
through the first multichannel tubes to the second manifold and to
separate the inlet flow from outlet flow exiting from the second
multichannel tubes into the first manifold.
13. The heat exchanger of claim 7, comprising a third manifold
disposed in a fluid path between the first and second manifolds,
wherein the first multichannel tubes direct flow from the first
manifold to the second manifold via the third manifold.
14. A heat exchanger comprising: a first manifold; a second
manifold; a plurality of first multichannel tubes in fluid
communication with the first manifold and the second manifold, each
first multichannel tube including a plurality of generally parallel
flow paths extending therethrough having a first configuration; a
plurality of second multichannel tubes in fluid communication with
the first manifold and the second manifold, each second
multichannel tube including a plurality of generally parallel flow
paths extending therethrough having a second configuration
different from the first configuration; and a pair of baffles in
the first manifold between the plurality of first multichannel
tubes and the plurality of second multichannel tubes to direct
circulation flow from an inlet side of the first manifold through
the plurality of first multichannel tubes to the second manifold
and therefrom through the plurality of second multichannel tubes to
an exit side of the first manifold, wherein the pair of baffles is
configured to isolate at least one multichannel tube between the
baffles of the pair, wherein the pair of baffles is disposed
between the plurality of first multichannel tubes and the plurality
of second multichannel tubes, and wherein the at least one
multichannel tube is isolated within the first manifold only;
wherein the second manifold is configured to direct a fluid exiting
the plurality of first multichannel tubes directly into both the at
least one isolated multichannel tube and the plurality of second
multichannel tubes.
15. The heat exchanger of claim 14, wherein the plurality of first
multichannel tubes are disposed adjacent to one another and the
plurality of second multichannel tubes are disposed adjacent to one
another.
16. The heat exchanger of claim 14, wherein the flow paths of the
first multichannel tubes are smaller than the flow paths of the
second multichannel tubes.
17. The heat exchanger of claim 14, wherein the flow paths of the
first multichannel tubes are of different cross-sectional shape
than the flow paths of the second multichannel tubes.
18. The heat exchanger of claim 14, wherein the first multichannel
tubes have more flow paths than the second multichannel tubes.
19. A method for promoting heat exchange to or from a fluid
comprising: introducing a fluid into an inlet side of a first
manifold of a heat exchanger; flowing the fluid through a first
plurality of multichannel tubes including a plurality of generally
parallel flow paths extending therethrough having a first
configuration; collecting the fluid in a second manifold; and
flowing the fluid from the second manifold to an outlet side of the
first manifold through a second plurality of multichannel tubes
including a plurality of generally parallel flow paths extending
therethrough having a second configuration different from the first
configuration; wherein the first plurality of multichannel tubes
are separated from the second plurality of multichannel tubes
within the first manifold by a pair of baffles isolating at least
one multichannel tube between the baffles of the pair within the
first manifold only and wherein the fluid exits the first plurality
of multichannel tubes and flows directly into both the at least one
isolated multichannel tube and the second plurality of multichannel
tubes.
20. A heating, ventilating, air conditioning or refrigeration
system comprising: a compressor configured to compress a gaseous
refrigerant; a condenser configured to receive and to condense the
compressed refrigerant; an expansion device configured to reduce
pressure of the condensed refrigerant; and an evaporator configured
to evaporate the refrigerant prior to returning the refrigerant to
the compressor; wherein at least one of the condenser and the
evaporator includes a heat exchanger having a first manifold, a
second manifold, a plurality of first multichannel tubes in fluid
communication with the first manifold and the second manifold, each
first multichannel tube including a plurality of generally parallel
flow paths extending therethrough having a first configuration, a
plurality of second multichannel tubes in fluid communication with
the first manifold and the second manifold, each second
multichannel tube including a plurality of generally parallel flow
paths extending therethrough having a second configuration
different from the first configuration, and a pair of baffles in
the first manifold to isolate at least one multichannel tube
between the baffles of the pair, wherein the pair of baffles is
disposed between the plurality of first multichannel tubes and the
plurality of second multichannel tubes, wherein the at least one
multichannel tube is isolated within the first manifold only, and
wherein the second manifold is configured to direct a fluid exiting
the plurality of first multichannel tubes directly into both the at
least one isolated multichannel tube and the plurality of second
multichannel tubes.
21. The system of claim 20, wherein the first plurality of
multichannel tubes is configured to de-superheat vaporized
refrigerant and the second plurality of multichannel tubes is
configured to subcool liquid refrigerant.
22. The system of claim 20, further comprising a reversing valve,
and wherein the heat exchanger functions as an evaporator in a heat
pump mode of operation and as a condenser in an air conditioning
mode of operation.
Description
BACKGROUND
The invention relates generally to multichannel heat exchangers
with dissimilar mulitchannel tubes.
Heat exchangers are used in heating, ventilation, air conditioning,
and refrigeration (HVAC&R) systems. Multichannel heat
exchangers generally include multichannel tubes for flowing
refrigerant through the heat exchanger. Each multichannel tube may
contain several individual flow channels. Fins may be positioned
between the tubes to facilitate heat transfer between refrigerant
contained within the tube flow channels and external air passing
over the tubes. Multichannel heat exchangers may be used in small
tonnage systems, such as residential systems, or in large tonnage
systems, such as industrial chiller systems.
In general, heat exchangers transfer heat by circulating a
refrigerant through a cycle of evaporation and condensation. In
many systems, the refrigerant changes phases while flowing through
heat exchangers in which evaporation and condensation occur. For
example, the refrigerant may enter an evaporator heat exchanger as
a liquid and exit as a vapor. In another example the refrigerant
may enter a condenser heat exchanger as a vapor and exit as a
liquid. These phase changes may result in both liquid and vapor
refrigerant flowing through the heat exchanger flow channels. In
particular, one portion of the heat exchanger may contain vapor
refrigerant undergoing de-superheating while another portion of the
heat exchanger contains a liquid undergoing subcooling.
The phase of the refrigerant may impact the efficiency of the heat
exchanger because different phases of refrigerant typically possess
different heat transfer properties. For example, vapor phase
refrigerant may pass through the flow channels at a higher velocity
than liquid phase refrigerant, resulting in less heat transfer
occurring for the tubes containing the vapor phase refrigerant. In
another example, employing a heat exchanger functioning as a
condenser, the vapor refrigerant may need to give off both latent
and sensible heat to become a liquid refrigerant while the liquid
refrigerant may need to give off only sensible heat to undergo
subcooling. In yet another example, the phase of the refrigerant
may affect the pressure drop that occurs within the flow channels.
In some systems, it may be desirable to minimize the pressure drop
by using an increased flow area, thereby improving system
efficiency.
SUMMARY
In accordance with aspects of the invention, a heat exchanger and a
system including a heat exchanger are presented. The heat exchanger
includes a first manifold, a second manifold, a first multichannel
tube in fluid communication with the manifolds that includes a
plurality of generally parallel flow paths with a first
configuration, and a second multichannel tube in fluid
communication with the manifolds that includes a plurality of
generally parallel flow paths with a second configuration that is
different from the first configuration.
In accordance with further aspects of the invention, a method for
promoting heat exchange to or from a fluid is presented. The method
includes introducing a fluid into an inlet side of a first manifold
of a heat exchanger, flowing fluid through a first plurality of
multichannel tubes, collecting fluid in a second manifold, and
flowing fluid through a second plurality of multichannel tubes to
an outlet side of the first manifold. The first plurality of
multichannel tubes includes a plurality of generally parallel flow
paths with a first configuration, and the second plurality of
multichannel tubes includes a plurality of generally parallel flow
paths with a second configuration different from the first
configuration.
DRAWINGS
FIG. 1 is a perspective view of an exemplary residential air
conditioning or heat pump system of the type that might employ a
heat exchanger.
FIG. 2 is a partially exploded view of the outside unit of the
system of FIG. 1, with an upper assembly lifted to expose certain
of the system components, including a heat exchanger.
FIG. 3 is a perspective view of an exemplary commercial or
industrial HVAC&R system that employs a chiller and air
handlers to cool a building and that may also employ heat
exchangers.
FIG. 4 is a diagrammatical overview of an exemplary air
conditioning system which may employ one or more heat exchangers
with internal tube configurations.
FIG. 5 is a diagrammatical overview of an exemplary heat pump
system which may employ one or more heat exchangers with internal
tube configurations.
FIG. 6 is a perspective view of an exemplary heat exchanger
containing internal tube configurations in accordance with one
aspect of the invention.
FIG. 7 is a detail perspective view of the heat exchanger of FIG. 6
sectioned through the first tubes.
FIG. 8 is a sectional view through one of the first tubes shown in
FIG. 7.
FIG. 9 is a detail perspective view of the heat exchanger of FIG. 6
sectioned through the second tubes.
FIG. 10 is a sectional view through one of the second tubes shown
in FIG. 9.
FIG. 11 is a sectional view of a further exemplary multichannel
tube.
FIG. 12 is a sectional view of another exemplary multichannel
tube.
FIG. 13 is a sectional view of still another exemplary multichannel
tube.
FIG. 14 is a detail perspective view of the heat exchanger of FIG.
6 with a manifold portion cut away.
FIG. 15 is a perspective view of an exemplary manifold in
accordance with aspects of the invention.
FIG. 16 is a top elevational view of the manifold of FIG. 15.
FIG. 17 is a perspective view of another exemplary manifold in
accordance with aspects of the invention.
FIG. 18 a perspective view of an exemplary compact heat exchanger
in accordance with aspects of the invention.
DETAILED DESCRIPTION
FIGS. 1-3 depict exemplary applications for heat exchangers. Such
systems, in general, may be applied in a range of settings, both
within the HVAC&R field and outside of that field. In presently
contemplated applications, however, heat exchanges may be used in
residential, commercial, light industrial, industrial and in any
other application for heating or cooling a volume or enclosure,
such as a residence, building, structure, and so forth. Moreover,
the heat exchanges may be used in industrial applications, where
appropriate, for basic refrigeration and heating of various fluids.
FIG. 1 illustrates a residential heating and cooling system. In
general, a residence, designated by the letter R, will be equipped
with an outdoor unit OU that is operatively coupled to an indoor
unit IU. The outdoor unit is typically situated adjacent to a side
of the residence and is covered by a shroud to protect the system
components and to prevent leaves and other contaminants from
entering the unit. The indoor unit may be positioned in a utility
room, an attic, a basement, and so forth. The outdoor unit is
coupled to the indoor unit by refrigerant conduits RC that transfer
primarily liquid refrigerant in one direction and primarily
vaporized refrigerant in an opposite direction.
When the system shown in FIG. 1 is operating as an air conditioner,
a coil in the outdoor unit serves as a condenser for recondensing
vaporized refrigerant flowing from indoor unit IU to outdoor unit
OU via one of the refrigerant conduits. In these applications, a
coil of the indoor unit, designated by the reference characters IC,
serves as an evaporator coil. The evaporator coil receives liquid
refrigerant (which may be expanded by an expansion device described
below) and evaporates the refrigerant before returning it to the
outdoor unit.
The outdoor unit draws in environmental air through sides as
indicated by the arrows directed to the sides of unit OU, forces
the air through the outer unit coil by a means of a fan (not shown)
and expels the air as indicated by the arrows above the outdoor
unit. When operating as an air conditioner, the air is heated by
the condenser coil within the outdoor unit and exits the top of the
unit at a temperature higher than it entered the sides. Air is
blown over indoor coil IC, and is then circulated through the
residence by means of ductwork D, as indicated by the arrows in
FIG. 1. The overall system operates to maintain a desired
temperature as set by a thermostat T. When the temperature sensed
inside the residence is higher than the set point on the thermostat
(plus a small amount), the air conditioner will become operative to
refrigerate additional air for circulation through the residence.
When the temperature reaches the set point (minus a small amount),
the unit will stop the refrigeration cycle temporarily.
When the unit in FIG. 1 operates as a heat pump, the roles of the
coils are simply reversed. That is, the coil of the outdoor unit
will serve as an evaporator to evaporate refrigerant and thereby
cool air entering the outdoor unit as the air passes over the
outdoor unit coil. Indoor coil IC will receive a stream of air
blown over it and will heat the air by condensing a
refrigerant.
FIG. 2 illustrates a partially exploded view of one of the units
shown in FIG. 1, in this case outdoor unit OU. In general, the unit
may be thought of as including an upper assembly UA made up of a
shroud, a fan assembly, a fan drive motor, and so forth. In the
illustration of FIG. 2, the fan and fan drive motor are not visible
because they are hidden by the surrounding shroud. An outdoor coil
OC is housed within this shroud and is generally deposed to
surround or at least partially surround other system components,
such as a compressor, an expansion device, a control circuit.
FIG. 3 illustrates another exemplary application, in this case an
HVAC&R system for building environmental management. A building
BL is cooled by a system that includes a chiller CH, which is
typically disposed on or near the building, or in an equipment room
or basement. Chiller CH is an air-cooled device that implements a
refrigeration cycle to cool water. The water is circulated to a
building through water conduits WC. The water conduits are routed
to air handlers AH at individual floors or sections of the
building. The air handlers are also coupled to ductwork DU that is
adapted to blow air from an outside intake OI.
Chiller CH, which includes heat exchangers for both evaporating and
condensing a refrigerant as described above, cools water that is
circulated to the air handlers. Air blown over additional coils
that receive the water in the air handlers causes the water to
increase in temperature and the circulated air to decrease in
temperature. The cooled air is then routed to various locations in
the building via additional ductwork. Ultimately, distribution of
the air is routed to diffusers that deliver the cooled air to
offices, apartments, hallways, and any other interior spaces within
the building. In many applications, thermostats or other command
devices (not shown in FIG. 3) will serve to control the flow of air
through and from the individual air handlers and ductwork to
maintain desired temperatures at various locations in the
structure.
FIG. 4 illustrates an air conditioning system 10, which uses
multichannel tubes. Refrigerant flows through the system within
closed refrigeration loop 12. The refrigerant may be any fluid that
absorbs and extracts heat. For example, the refrigerant may be
hydrofluorocarbon (HFC) based R-410A, R-407, or R-134a, or it may
be carbon dioxide (R-744a) or ammonia (R-717). Air conditioning
system 10 includes control devices 14 that enable system 10 to cool
an environment to a prescribed temperature.
System 10 cools an environment by cycling refrigerant within closed
refrigeration loop 12 through condenser 16, compressor 18,
expansion device 20, and evaporator 22. The refrigerant enters
condenser 16 as a high pressure and temperature vapor and flows
through the multichannel tubes of condenser 16. A fan 24, which is
driven by a motor 26, draws air across the multichannel tubes. Fan
24 may push or pull air across the tubes. Heat transfers from the
refrigerant vapor to the air producing heated air 28 and causing
the refrigerant vapor to condense into a liquid. The liquid
refrigerant then flows into an expansion device 20 where the
refrigerant expands to become a low pressure and temperature
liquid. Typically, expansion device 20 will be a thermal expansion
valve (TXV); however, in other embodiments, the expansion device
may be an orifice or a capillary tube. After the refrigerant exits
the expansion device, some vapor refrigerant may be present in
addition to the liquid refrigerant.
From expansion device 20, the refrigerant enters evaporator 22 and
flows through the evaporator multichannel tubes. A fan 30, which is
driven by a motor 32, draws air across the multichannel tubes. Heat
transfers from the air to the refrigerant liquid producing cooled
air 34 and causing the refrigerant liquid to boil into a vapor. In
some embodiments, the fan may be replaced by a pump that draws
fluid across the multichannel tubes.
The refrigerant then flows to compressor 18 as a low pressure and
temperature vapor. Compressor 18 reduces the volume available for
the refrigerant vapor, consequently, increasing the pressure and
temperature of the vapor refrigerant. The compressor may be any
suitable compressor such as a screw compressor, reciprocating
compressor, rotary compressor, swing link compressor, scroll
compressor, or turbine compressor. Compressor 18 is driven by a
motor 36 that receives power from a variable speed drive (VSD) or a
direct AC or DC power source. In one embodiment, motor 36 receives
fixed line voltage and frequency from an AC power source although
in some applications the motor may be driven by a variable voltage
or frequency drive. The motor may be a switched reluctance (SR)
motor, an induction motor, an electronically commutated permanent
magnet motor (ECM), or any other suitable motor type. The
refrigerant exits compressor 18 as a high temperature and pressure
vapor that is ready to enter the condenser and begin the
refrigeration cycle again.
The operation of the refrigeration cycle is governed by control
devices 14 that include control circuitry 38, an input device 40,
and a temperature sensor 42. Control circuitry 38 is coupled to
motors 26, 32, and 36 that drive condenser fan 24, evaporator fan
30, and compressor 18, respectively. The control circuitry uses
information received from input device 40 and sensor 42 to
determine when to operate motors 26, 32, and 36 that drive the air
conditioning system. In some applications, the input device may be
a conventional thermostat. However, the input device is not limited
to thermostats, and more generally, any source of a fixed or
changing set point may be employed. These may include local or
remote command devices, computer systems and processors,
mechanical, electrical and electromechanical devices that manually
or automatically set a temperature-related signal that the system
receives. For example, in a residential air conditioning system,
the input device may be a programmable 24-volt thermostat that
provides a temperature set point to the control circuitry. Sensor
42 determines the ambient air temperature and provides the
temperature to control circuitry 38. Control circuitry 38 then
compares the temperature received from the sensor to the
temperature set point received from the input device. If the
temperature is higher than the set point, control circuitry 38 may
turn on motors 26, 32, and 36 to run air conditioning system 10.
The control circuitry may execute hardware or software control
algorithms to regulate the air conditioning system. In some
embodiments, the control circuitry may include an analog to digital
(A/D) converter, a microprocessor, a non-volatile memory, and an
interface board. Other devices may, of course, be included in the
system, such as additional pressure and/or temperature transducers
or switches that sense temperatures and pressures of the
refrigerant, the heat exchangers, the inlet and outlet air, and so
forth.
FIG. 5 illustrates a heat pump system 44 that uses multichannel
tubes. Because the heat pump may be used for both heating and
cooling, refrigerant flows through a reversible
refrigeration/heating loop 46. The refrigerant may be any fluid
that absorbs and extracts heat. The heating and cooling operations
are regulated by control devices 48.
Heat pump system 44 includes an outside coil 50 and an inside coil
52 that both operate as heat exchangers. The coils may function
either as an evaporator or as a condenser depending on the heat
pump operation mode. For example, when heat pump system 44 is
operating in cooling (or "AC") mode, outside coil 50 functions as a
condenser, releasing heat to the outside air, while inside coil 52
functions as an evaporator, absorbing heat from the inside air.
When heat pump system 44 is operating in heating mode, outside coil
50 functions as an evaporator, absorbing heat from the outside air,
while inside coil 52 functions as a condenser, releasing heat to
the inside air. A reversing valve 54 is positioned on reversible
loop 46 between the coils to control the direction of refrigerant
flow and thereby to switch the heat pump between heating mode and
cooling mode.
Heat pump system 44 also includes two metering devices 56 and 58
for decreasing the pressure and temperature of the refrigerant
before it enters the evaporator. The metering device also acts to
regulate refrigerant flow into the evaporator so that the amount of
refrigerant entering the evaporator equals the amount of
refrigerant exiting the evaporator. The metering device used
depends on the heat pump operation mode. For example, when heat
pump system 44 is operating in cooling mode, refrigerant bypasses
metering device 56 and flows through metering device 58 before
entering the inside coil 52, which acts as an evaporator. In
another example, when heat pump system 44 is operating in heating
mode, refrigerant bypasses metering device 58 and flows through
metering device 56 before entering outside coil 50, which acts as
an evaporator. In other embodiments, a single metering device may
be used for both heating mode and cooling mode. The metering
devices typically are thermal expansion valves (TXV), but also may
be orifices or capillary tubes.
The refrigerant enters the evaporator, which is outside coil 50 in
heating mode and inside coil 52 in cooling mode, as a low
temperature and pressure liquid. Some vapor refrigerant also may be
present as a result of the expansion process that occurs in
metering device 56 or 58. The refrigerant flows through
multichannel tubes in the evaporator and absorbs heat from the air
changing the refrigerant into a vapor. In cooling mode, the indoor
air passing over the multichannel tubes also may be dehumidified.
The moisture from the air may condense on the outer surface of the
multichannel tubes and consequently be removed from the air.
After exiting the evaporator, the refrigerant passes through
reversing valve 54 and into compressor 60. Compressor 60 decreases
the volume of the refrigerant vapor, thereby, increasing the
temperature and pressure of the vapor. The compressor may be any
suitable compressor such as a screw compressor, reciprocating
compressor, rotary compressor, swing link compressor, scroll
compressor, or turbine compressor.
From the compressor, the increased temperature and pressure vapor
refrigerant flows into a condenser, the location of which is
determined by the heat pump mode. In cooling mode, the refrigerant
flows into outside coil 50 (acting as a condenser). A fan 62, which
is powered by a motor 64, draws air over the multichannel tubes
containing refrigerant vapor. In some embodiments, the fan may be
replaced by a pump that draws fluid across the multichannel tubes.
The heat from the refrigerant is transferred to the outside air
causing the refrigerant to condense into a liquid. In heating mode,
the refrigerant flows into inside coil 52 (acting as a condenser).
A fan 66, which is powered by a motor 68, draws air over the
multichannel tubes containing refrigerant vapor. The heat from the
refrigerant is transferred to the inside air causing the
refrigerant to condense into a liquid.
After exiting the condenser, the refrigerant flows through the
metering device (56 in heating mode and 58 in cooling mode) and
returns to the evaporator (outside coil 50 in heating mode and
inside coil 52 in cooling mode) where the process begins again.
In both heating and cooling modes, a motor 70 drives compressor 60
and circulates refrigerant through reversible refrigeration/heating
loop 46. The motor may receive power either directly from an AC or
DC power source or from a variable speed drive (VSD). The motor may
be a switched reluctance (SR) motor, an induction motor, an
electronically commutated permanent magnet motor (ECM), or any
other suitable motor type.
The operation of motor 70 is controlled by control circuitry 72.
Control circuitry 72 receives information from an input device 74
and sensors 76, 78, and 80 and uses the information to control the
operation of heat pump system 44 in both cooling mode and heating
mode. For example, in cooling mode, input device 74 provides a
temperature set point to control circuitry 72. Sensor 80 measures
the ambient indoor air temperature and provides it to control
circuitry 72. Control circuitry 72 then compares the air
temperature to the temperature set point and engages compressor
motor 70 and fan motors 64 and 68 to run the cooling system if the
air temperature is above the temperature set point. In heating
mode, control circuitry 72 compares the air temperature from sensor
80 to the temperature set point from input device 74 and engages
motors 64, 68, and 70 to run the heating system if the air
temperature is below the temperature set point.
Control circuitry 72 also uses information received from input
device 74 to switch heat pump system 44 between heating mode and
cooling mode. For example, if input device 74 is set to cooling
mode, control circuitry 72 will send a signal to a solenoid 82 to
place reversing valve 54 in air conditioning position 84.
Consequently, the refrigerant will flow through reversible loop 46
as follows: the refrigerant exits compressor 60, is condensed in
outside coil 50, is expanded by metering device 58, and is
evaporated by inside coil 52. If the input device is set to heating
mode, control circuitry 72 will send a signal to solenoid 82 to
place reversing valve 54 in heat pump position 86. Consequently,
the refrigerant will flow through the reversible loop 46 as
follows: the refrigerant exits compressor 60, is condensed in
inside coil 52, is expanded by metering device 56, and is
evaporated by outside coil 50.
The control circuitry may execute hardware or software control
algorithms to regulate the heat pump system 44. In some
embodiments, the control circuitry may include an analog to digital
(A/D) converter, a microprocessor, a non-volatile memory, and an
interface board.
The control circuitry also may initiate a defrost cycle when the
system is operating in heating mode. When the outdoor temperature
approaches freezing, moisture in the outside air that is directed
over outside coil 50 may condense and freeze on the coil. Sensor 76
measures the outside air temperature, and sensor 78 measures the
temperature of outside coil 50. These sensors provide the
temperature information to the control circuitry which determines
when to initiate a defrost cycle. For example, if either of sensors
76 or 78 provides a temperature below freezing to the control
circuitry, system 44 may be placed in defrost mode. In defrost
mode, solenoid 82 is actuated to place reversing valve 54 in air
conditioning position 84, and motor 64 is shut off to discontinue
air flow over the multichannels. System 44 then operates in cooling
mode until the increased temperature and pressure refrigerant
flowing through outside coil 50 defrosts the coil. Once sensor 78
detects that coil 50 is defrosted, control circuitry 72 returns the
reversing valve 54 to heat pump position 86. As will be appreciated
by those skilled in the art, the defrost cycle can be set to occur
at many different time and temperature combinations.
FIG. 6 is a perspective view of an exemplary heat exchanger, which
may be used in an air conditioning system 10 or a heat pump system
44. The exemplary heat exchanger may be a condenser 16, an
evaporator 22, an outside coil 50, or an inside coil 52, as shown
in FIGS. 1 and 2. It should also be noted that in similar or other
systems, the heat exchanger may be used as part of a chiller or in
any other heat exchanging application. The heat exchanger includes
manifolds 88 and 90 that are connected by multichannel tubes 92.
Although 30 tubes are shown in FIG. 6, the number of tubes may
vary. The manifolds and tubes may be constructed of aluminum or any
other material that promotes good heat transfer. Refrigerant flows
from the manifold 88 through first tubes 94 to the manifold 90. The
refrigerant then returns to the manifold 88 through second tubes
96. In some embodiments, the heat exchanger may be rotated
approximately 90 degrees so that the multichannel tubes run
vertically between a top manifold and a bottom manifold. The heat
exchanger may be inclined at an angle relative to the vertical.
Furthermore, although the multichannel tubes are depicted as having
an oblong shape, the tubes may be any shape, such as tubes with a
cross-section in the form of a rectangle, square, circle, oval,
ellipse, triangle, trapezoid, or parallelogram. In some
embodiments, the tubes may have a diameter ranging from 0.5 mm to 3
mm. It should also be noted that the heat exchanger may be provided
in a single plane or slab, or may include bends, corners, contours
and so forth.
Refrigerant enters the heat exchanger through an inlet 98 and exits
the heat exchanger through an outlet 100. Although FIG. 6 depicts
the inlet at the top of manifold and the outlet at the bottom of
the manifold, the inlet and outlet positions may be interchanged so
that the fluid enters at the bottom and exits at the top. The fluid
also may enter and exit the manifold from multiple inlets and
outlets positioned on bottom, side, or top surfaces of the
manifold. Baffles 102 separate the inlet 98 and outlet 100 portions
of the manifold 88. Although a double baffle is illustrated, any
number of one or more baffles may be employed to create separation
of the inlet 98 and the outlet 100.
In a typical heat exchanger application, refrigerant may enter
manifold 88 in one phase and exit the manifold 88 in another phase.
For example, if the heat exchanger operates as a condenser,
refrigerant may enter inlet 98 as a vapor. As the vapor travels
through first multichannel tubes 94, the vapor releases heat to the
outside environment causing the vapor to desuperheat and condense
into a liquid. Then, as the liquid refrigerant travels through
second multichannel tubes 96, the liquid releases heat to the
outside environment causing subcooling. First tubes 94 may have a
different internal configuration than second tubes 96 to maximize
the heat transfer properties of the refrigerant when it is in the
vapor phase and when it is in the liquid phase.
Fins 104 are located between multichannel tubes 92 to promote the
transfer of heat between tubes 92 and the environment. In one
embodiment, the fins are constructed of aluminum, brazed or
otherwise joined to the tubes, and disposed generally perpendicular
to the flow of refrigerant. However, in other embodiments the fins
may be made of other materials that facilitate heat transfer and
may extend parallel or at varying angles with respect to the flow
of the refrigerant. The fins may be louvered fins, corrugated fins,
or any other suitable type of fin.
FIG. 7 shows the heat exchanger of FIG. 6 sectioned through first
tubes 94 to illustrate the internal configuration of the first
tubes. Refrigerant flows through flow channels 106 formed within
the tubes. The direction of fluid flow 108 is from manifold 88
shown in FIG. 6 to manifold 90. As the refrigerant flows toward
manifold 90, the refrigerant begins, or continues to, change
phases. For example, in a condenser, the vapor refrigerant releases
heat to the outside air, is de-superheated, and begins to change
from a vapor to a liquid. Likewise, in an evaporator, the liquid
refrigerant absorbs heat from the outside air and begins to change
from a liquid to a vapor.
FIG. 8 is a sectional view through one of the first tubes 94 shown
in FIG. 7. In the illustrated embodiment, flow channels 106 have a
round cross-section with a small diameter relative to the width A
and height B of the first tubes. In one embodiment, these small
diameter flow channels may be used in a condenser configuration to
increase the surface area for heat transfer. It should be noted
that other flow path shapes may be used, and these may be separated
by internal walls that are straight and continuous, or profiles and
interruptions may be provided in the walls. Moreover, in a
presently contemplated embodiment, the number of parallel flow
paths formed in the first tubes may range from 16 to 24, although
other numbers may be provided.
As illustrated in FIG. 9, the refrigerant returns from manifold 90
through flow channels 114 of the second tubes. The direction of
fluid flow 116 is from manifold 90 to manifold 88 shown in FIG. 6.
In some embodiments, the refrigerant flowing through the second
tubes 96 has already changed phase. For example, in a condenser,
the refrigerant may be in the liquid phase (and continues to be
subcooled in the second tubes), and in an evaporator, the
refrigerant may be in the vapor phase.
FIG. 10 is a sectional view through one of the second tubes 96
shown in FIG. 9. Flow channels 114 have a square cross-section that
is larger than the cross-section of flow channels 106, shown in
FIG. 8. In one embodiment, these larger diameter flow channels may
be used in a condenser configuration to minimize the pressure drop
that occurs for the vapor phase refrigerant. It should be noted
that the particular shape, size and number of the flow paths in the
second tubes may be varied.
FIGS. 11, 12, and 13 depict other exemplary cross-sectional shapes
that flow channels may have. It should be noted, however, that the
shapes shown throughout the figures are not intended to be
limiting, and other optimized shapes, sizes, configurations and
numbers of flow paths may be provided. FIG. 11 illustrates an
alternate tube 118 having flow channels 120 of a rectangular shape.
FIG. 12 illustrates an alternate tube 122 having flow channels 124
of a longer rectangular shape. FIG. 13 illustrates an alternate
tube 126 with one large flow channel 128. Alternate tube 126 may be
used in a tube section of the heat exchanger or additionally, it
may be positioned as the bottom tube in a heat exchanger to act as
a receiver section for excess refrigerant.
Any combination of internal tube configurations may be used in
accordance with the present techniques to optimize performance of
the heat exchanger. For example, the first tubes may be configured
as depicted in FIG. 11 while the second tubes may be configured as
depicted in FIG. 13. Furthermore, the number of flow channels
present in the first set of tubes may differ from the number of
flow channels present in the second set of tubes. In one
embodiment, the internal configuration of the first tubes may be
selected based on heat transfer properties for de-superheating
vapor phase refrigerant and the internal configuration of the
second tubes may be selected based on heat transfer properties for
subcooling liquid phase refrigerant.
Moreover, it should be noted that the particular shape and
cross-sectional area of the flow channels may be adapted for
specific flow and heat transfer goals of the heat exchanger. For
example, a greater number of smaller flow channels will generally
have a smaller cumulative cross sectional area then a lesser number
of larger flow channels. The resulting flow rates (and flow
velocities) and consequent thermal transfer rates may be thus
altered, and certain flow rates and velocities may be preferred for
vapor phase flow, liquid phase flow or mixed phase flow.
FIG. 14 illustrates a perspective view of the heat exchanger shown
in FIG. 6 with a portion of manifold 88 cut away to show the
manifold interior. Note that the fins have been removed for
clarity. As shown, the refrigerant exits manifold 88 through first
tubes 94 and returns to manifold 88 through second tubes 96.
Baffles 102 divide the first tube section of the manifold from the
second tube section. The refrigerant in the first tube section of
the manifold may be a different phase than the refrigerant in the
second tube section. The baffles 102 are spaced apart at a distance
C to create a volume 132 within the manifold that provides
additional insulation between the two sections of the manifold and
to provide redundancy in the event one of the baffles is punctured
or otherwise develops a leak. In some embodiments, an isolated tube
134 may be placed in between baffles 102 to provide separation
between first tubes 94 and second tubes 96.
Referring to FIG. 15, other embodiments may include a double
manifold 136. Double manifold 136 has a reduced width D which
allows for increased capacity in a heat exchanger having width
restrictions. Double manifold 140 has a cap 140 which may be placed
over an end to contain the refrigerant. In some embodiments, cap
140 may be placed within the manifold to act as a baffle.
FIG. 16 is an elevational view of the manifold of FIG. 15 that
depicts two end shapes for tubes 94. Tubes 94 may have an end shape
142 that follows the curvature of manifold 136. Alternatively, the
tubes may have a traditional flat end shape 144. The tubes used in
a heat exchanger may be any combination of the disclosed end
shapes. In other embodiments, the end shapes may be used in heat
exchangers with single manifolds.
FIG. 17 is a perspective view of an alternative double manifold
146. A cap 148 may be placed over an end to contain the
refrigerant. The end shapes of the tubes 94 may be flat or may
follow the curvature of the manifold.
In addition to increasing capacity within a small width, double
manifolds 136 and 146 may be used to provide support for coils in
compact heat exchangers. FIG. 18 is a perspective view of an
exemplary compact heat exchanger 150. Note that the fins have been
removed for clarity. Double manifolds 136 connect curved coil
sections 152 allowing a heat exchanger to be constructed in a
circular shape. Baffles 102 may be present within manifolds 136 to
separate the refrigerant vapor phase from the refrigerant liquid
phase. In other embodiments, double manifolds may be used to
construct heat exchangers in other configurations such as
rectangular, square, hexagonal, or semi-circular shapes.
The tube configurations described herein may find application in a
variety of heat exchangers and HVAC&R systems containing heat
exchangers. However, the configurations are particularly
well-suited to evaporators used in residential air conditioning and
heat pump systems where there is a need to tailor the heat transfer
properties for the liquid and vapor refrigerant phases. The
configurations are intended to improve heat exchanger efficiency by
allowing customization of tubes for the de-superheating process and
subcooling process.
It should be noted that the present discussion makes use of the
term "multichannel" tubes or "multichannel heat exchanger" to refer
to arrangements in which heat transfer tubes include a plurality of
flow paths between manifolds that distribute flow to and collect
flow from the tubes. A number of other terms may be used in the art
for similar arrangements. Such alternative terms might include
"microchannel" and "microport." The term "microchannel" sometimes
carries the connotation of tubes having fluid passages on the order
of a micrometer and less. However, in the present context such
terms are not intended to have any particular higher or lower
dimensional threshold. Rather, the term "multichannel" used to
describe and claim embodiments herein is intended to cover all such
sizes. Other terms sometimes used in the art include "parallel
flow" and "brazed aluminum." However, all such arrangements and
structures are intended to be included within the scope of the term
"multichannel." In general, such "multichannel" tubes will include
flow paths disposed along the width or in a plane of a generally
flat, planar tube, although, again, the invention is not intended
to be limited to any particular geometry unless otherwise specified
in the appended claims.
While only certain features of the invention have been illustrated
and described herein, many modifications and changes will occur to
those skilled in the art. It is, therefore, to be understood that
the appended claims are intended to cover all such modifications
and changes as fall within the true spirit of the invention.
Furthermore, in an effort to provide a concise description of the
exemplary embodiments, all features of an actual implementation may
not have been described. It should be appreciated that in the
development of any such actual implementation, as in any
engineering or design project, numerous implementation specific
decisions must be made. Such a development effort might be complex
and time consuming, but would nevertheless be a routine undertaking
of design, fabrication, and manufacture for those of ordinary skill
having the benefit of this disclosure.
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